Objective
The objective of this project is to design and construct a mechanical oscillator apparatus to be used for the study of ice accumulation on super-hydrophobic surfaces. The apparatus will be integrated into the test chamber of the icing wind tunnel located in the Nano and Microfluidics Laboratory at Stevens Institute of Technology.
Background
Ice accretion is problematic for many mechanical systems that are subjected to cold and moist operating conditions. For example, the buildup of ice on the blades of wind driven turbines causes unwanted drag that reduces the efficiency of electricity generation. Also, the weight of accumulated ice on high voltage cross-country transmission lines can sometimes overload their support towers to the point of collapse. Further, formation of ice on aircraft wings can lead to disastrous loss of lift.
Presently, there is widespread interest in the mechanical engineering and material science communities to develop treatments and/or textures for surfaces that can reduce or even eliminate the phenomenon of icing upon exposure to winter weather conditions. The Nano- and Micro- Fluidics Laboratory at Stevens Institute of Technology is becoming a leader in this field of research, having recently completed the construction of a refrigerated wind tunnel that can direct a moisture laden airstream onto sub 0°C specimens having any of a variety of surface structures. The Stevens Icing Wind Tunnel provides capability for the controlled accretion of ice onto samples placed within a test chamber. The purpose of the present project has been the integration of apparatus into this chamber to advance the test capability of the system.
Presently, there is widespread interest in the mechanical engineering and material science communities to develop treatments and/or textures for surfaces that can reduce or even eliminate the phenomenon of icing upon exposure to winter weather conditions. The Nano- and Micro- Fluidics Laboratory at Stevens Institute of Technology is becoming a leader in this field of research, having recently completed the construction of a refrigerated wind tunnel that can direct a moisture laden airstream onto sub 0°C specimens having any of a variety of surface structures. The Stevens Icing Wind Tunnel provides capability for the controlled accretion of ice onto samples placed within a test chamber. The purpose of the present project has been the integration of apparatus into this chamber to advance the test capability of the system.
The surfaces of interest are those having the superhydrophobic characteristic of extreme water repellency. Impinging droplets bead-up and roll off such surfaces, thereby preventing the condensation of a film of water. Shown below is a Scanning Electron Microscope image of a typical superhydrophobic surface having a periodicity of about 1 μm between adjacent narrow pit features.
Air trapped in the deep pits allows the overlying water droplets to float above the textured topography. The surface tension of each individual droplet forces it into a nearly spherical shape as pictured in the side-view photograph below.
The icephobic properties of such surfaces remain largely unknown. A near term goal of the Nano- and Micro- Fluidics Laboratory is to study the degree to which superhydrophobic surfaces retard the formation and reduce the adhesion of ice.
A previous senior design project resulted in the construction of a centrifuge-based system. Its installation within the test chamber of the Stevens Icing Wind Tunnel is shown below.
A previous senior design project resulted in the construction of a centrifuge-based system. Its installation within the test chamber of the Stevens Icing Wind Tunnel is shown below.
The centrifuge apparatus has enabled the measurement of the shear force needed to shed ice from a superhydrophobic sample mounted on a rotating arm whose speed was gradually increased and monitored until the ice detached. The centrifuge arm spins on an axis aligned parallel to the flow of the cold moist air flows (which is from lower right to upper left in the above photograph).
The present senior design project aims to construct an in-situ wind tunnel system that complements the existing rotational system. The new apparatus utilizes instead the restoring force of simple harmonic oscillations to study how vibratory motion affects the accumulation of ice on superhydrophobic surfaces.
The present senior design project aims to construct an in-situ wind tunnel system that complements the existing rotational system. The new apparatus utilizes instead the restoring force of simple harmonic oscillations to study how vibratory motion affects the accumulation of ice on superhydrophobic surfaces.